I never realised the speed was actually printed on the PIC. I just =
assumed
all PICs could run up to speed listed in their respective datasheets.

The electronics hobby shop I bought my PICs from didn't specify if its =
was
4Mhz or 20Mhz. I've run all 5 my 628's, 877's and 876's I've bought =
there at
20Mhz without any problems.

I just checked though, and they're all -4 chips! (-04/P, 04/SP) I'm even
using them in my DIY Wisp628 :-). Guess I just got lucky.=20

The 18F's I got are all marked -I/SP, does that mean they can run at all
specified frequencies in the datasheet?

_____ =20

Andr=E9 Miller =09


-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU] On
Behalf Of Jinx
Sent: 19 March 2004 11:31 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC:] PIC 16F628 an 20 MHz

> Does someone knows if the maximal frequency printed on a chip=20
> determines an ability of the oscilator circuit too?

It used to be the case, probably still is, that all 628s (for example) =
come
from the same stock

They are then tested and sorted for GUARANTEED operation at the speed
limits. A device in the 4MHz pile may run at 10MHz or even 15MHz, but IT =
IS
guaranteed to run properly under all conditions at 4MHz. Some 20MHz =
devices
may run at 25MHz, but probably not under all conditions. On an =
individual
basis you could get lucky, but it's not something you'd want to expect =
from
a production run using such a PIC unless every unit was speed tested

Economics plays a part too. Operation speed is a factor in pricing, so =
is
demand for a particular speed. Parts that are capable of spec operation =
at
10MHz and 20MHz might be re-branded as 4MHz to satisfy a market

--
http://www.piclist.com hint: The PICList is archived three different =
ways.
See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.